Hypertensive diseases in pregnancy

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Chapter 14 Hypertensive diseases in pregnancy

Between 5 and 8% of pregnancies are complicated by hypertensive diseases. These are gestational hypertension, pre-eclampsia, chronic hypertension, essential and secondary and superimposed pre-eclampsia.

CLASSIFICATION

Gestational hypertension

Gestational hypertension is classified as hypertension that arises after 20 weeks’ gestation without any of the other features of pre-eclampsia and resolves within 3 months of delivery.

Pre-eclampsia

Pre-eclampsia is a multisystem disorder; hypertension is usually the first manifestation, followed by proteinuria. The clinical diagnosis of pre-eclampsia requires the onset after 20 weeks’ gestation of hypertension and one or more of:

• Proteinuria – >300 mg/24 h or urine protein/creatinine ratio >30 mg/mmol

• Renal insufficiency – serum/plasma creatinine >0.09 mmol/L or oliguria

• Liver disease – raised serum transaminases and/or severe epigastric/right upper quadrant pain

• Neurological problems – convulsions (eclampsia); hyperreflexia with clonus; severe headaches with hyperreflexia; persistent visual disturbances (scotomata)

• Haematological disturbances – thrombocytopenia; disseminated intravascular coagulation; haemolysis

• Fetal growth restriction.

The hypertension of pre-eclampsia returns to normal within 3 months of delivery.

Chronic hypertension

• Essential hypertension: blood pressure ≥140 mmHg systolic and/or ≥90 mmHg diastolic (K5) prior to conception or in the first half of pregnancy without an apparent underlying cause.

• Secondary hypertension: hypertension associated with renal, renovascular and endocrine disorders and aortic coarctation.

Pre-eclampsia superimposed on chronic hypertension

This is diagnosed when one or more of the systemic features of pre-eclampsia develops after 20 weeks, i.e. in addition to a rise in blood pressure and/or a sudden increase in protein excretion.

GESTATIONAL HYPERTENSION

Pregnancies complicated by gestational hypertension have a good prognosis. The blood pressure should be carefully monitored and this can normally be done in a Day Assessment Unit or with ambulatory home blood pressure monitoring. Careful surveillance should be maintained to exclude the development of pre-eclampsia.

If the blood pressure exceeds 140/90 then antihypertensive therapy, as detailed in Table 14.1, is commenced, with the objective of maintaining the systolic pressure between 110 and 140 mmHg and the diastolic between 80 and 90 mmHg.

Table 14.1 Summary of the management of pregnancy-induced hypertension

Classification	Observations	Treatment
Gestational hypertension	Report rise in blood pressure or excessive weight gain to obstetrician	Assess in day assessment unit or ambulatory blood pressure monitoring at home
Moderate pre-eclampsia	In hospital: Four-hourly recording of the blood pressure Twice-daily urine testing for protein Regular observation of the patient’s condition, including fluid intake and output Bed rest, but toilet privileges allowed

Admit to hospital

Sedation (if indicated)

Methyldopa (starting) 250 mg two to three time daily increasing to max. 3 g daily

Labetalol (starting) 100 mg twice daily or atenolol (starting) 100 mg in evening or oxprenolol (starting) 20 mg three times daily or methyldopa (starting) 250 mg three times daily

Nifedipine 10–20 mg twice daily to max. 40 mg b.d.

Severe pre-eclampsia

Two-hourly blood pressure recording for 6 hours, then 4-hourly

Urine testing for protein twice daily

Fluid intake and output recorded

Careful observation of the patient for the signs of imminent eclampsia

Complete bed rest for 24 hours, thereafter possible toilet privileges

Admit to hospital

Depending on the severity of the illness give:

a. Magnesium sulphate (see p. 121).

b. Hydralazine – start 5–10 mg IV slowly, repeat 20–30 min. Continue infusion 50–300 μg/min, rate to keep BP around 140/90

Imminent eclampsia

The patient requires careful systematic observation as eclampsia is a possible outcome

The blood pressure requires frequent estimation, at intervals determined by the obstetrician

Fluid intake and urinary output must be measured meticulously, and the urine tested quantitatively for protein

Magnesium sulphate (see p. 121).

Hydralazine intravenously

Caesarean section

PRE-ECLAMPSIA

Pathogenesis

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